BikeBiz Bicycle and cycling retail news
Dr. Borut Fonda, lead scientist at absoluteBLACK’s Science Lab, tells us how oval rings can benefit all
Oval rings are not a new concept. How are absoluteBLACK oval chainrings different from those from the past?
Oval chainrings have been around for over 100 years, but Biopace chainrings are what most people still remember for delivering weird pedalling motion, and some even reported knee pain. In fact, Biopace somehow became an umbrella synonym to all non-round chainrings including ‘oval’.
Interestingly, Biopace was not even oval but a complex, non-round shape with completely missed timing of the major axis (i.e. crank position when the chainring’s diameter is the biggest). In their case, the major axis of the chainring was oriented when the crank was at the bottom and top position, whereas absoluteBLACK oval chainrings exhibit major axis at about a 109° crank angle. This is a night and day difference between the two chainrings.
You mentioned knee pain with Biopace chainrings. Do absoluteBLACK’s ovals suffer from the same problem?
The reason for the knee pain was simply wrong orientation of the ‘oval’ shape and most importantly, timing. Some of the biggest contributing factors for the knee pain are shear forces between the tibia and the patella and compressive forces between the patella and femur, resulting in an anterior knee pain, which is the most reported injury in cyclists.
Biopace’s unfortunate design emphasised a load at points where some of the knee shear forces are the largest. absoluteBLACK oval chainrings are designed to perfectly fit specific riding styles and involve the hip joint to a larger extent, which essentially takes the load off the knee. When looking at the general knee load during cycling, it peaks at around a 70° crank angle, while the hip peaks well beyond 90°.
absoluteBLACK oval chainrings’ majors axis orientation is at around a 109° crank. This matches the power profile of a cyclist to reduce power losses and transfers the load from the knee to the hip. Increasing the chainring diameter at the points where the cyclists are the strongest results in a more controlled push on the pedal, which can consequently be seen as lower varus/valgus moments (less lateral sway from the knees).
Shimano had a great idea, but the implementation didn’t quite work out. At the time of making them, there was no precise equipment capable of measuring all the forces applied to the pedal, measuring body response, forces on the knees etc. At that time, even the automotive industry was hiring dozens of mathematicians who were calculating stress forces on the car parts with pen and paper. Even today, it’s still tricky (especially knee load measurements) and only a handful of universities and private companies possess equipment capable of measuring those forces accurately. That’s why most of them over the last ten years focused on researching the power gains with oval rings instead of looking into efficiency/effectiveness gains.
What does it take to measure all those forces?
The most important part of equipment is a force pedal system with an ability to measure six force/torque components at the pedals (three forces and three torques). This system must be synchronised with a complete 3D motion-capturing system that allows acquiring motion of the body segments. By using some advanced algorithms for inverse dynamics, we can calculate joint loads for the lower extremity.
At our absoluteBLACK Science Lab, we have all the mentioned technological capabilities plus a lot more, which allows us to design all our chainrings based on objective scientific data. We have performed over several thousand measurements on different riding styles to come up with the designs we have now.
Certain riders are pretty convinced ovals can give you more power, but you mentioned that there are gains in efficiency instead. Can you elaborate on that?
We need to first set the correct terminology. ‘More power’ can be appropriately interpreted by achieving a higher maximum power output during an all-out sprint. Although it has been shown in the past that oval chainrings can improve sprinting performance, this is not the main performance benefit.
So, going back to the original question of what cyclists are referring to, it is actually the effectiveness of pedalling and efficiency.
With the absoluteBLACK oval chainrings, we demonstrated that cyclists exhibit a 9% more effective pedal stroke by applying less force to the pedal that doesn’t contribute to power. Essentially, they generate less muscular force for a given power output. This allows them to pedal at higher power outputs with the same effort as before. All that also results in improved efficiency, which is a metabolic measure (i.e. ratio between the mechanical work and energy expenditure). We have shown that cyclists improve their efficiency when using absoluteBLACK oval chainrings.
I’ve heard on many occasions that ovals can deliver ‘rounder than round’ pedalling sensation. Is this even possible?
Great question. Indeed, after a few rides, you start getting the sensation that the pedal stroke becomes more fluid or smooth. This is mainly the consequence of your power profile, which is not constant. Humans are not designed to deliver equal torque/profile throughout the pedal stroke and hence the power peaks where the sum of all muscular and non-muscular (inertia and leg weight) components result in the largest power. During seated road cycling, we see that peak at around 109° of crank angle. Matching the chainring’s diameter to that power profile results in smoother pedalling.
Are they for everyone?
Simple question, tricky answer. We designed our oval chainrings to improve cyclists’ abilities to pedal easier on the uphills, go faster, get less tired, put less load on the knees and have more fun on the bike. This all comes back to the effectiveness of pedalling I mentioned before. The more you train, the better your pedal stroke becomes. The problem we have in today’s world is that we all have busy lives and only a handful of people can actually afford to ride for more than 12 hours a week for years to get the near-perfect pedal stroke. These lucky ones are mostly professional or very serious riders.
We can’t improve their pedal stroke a lot as it’s already very good, so in this category, it’s mainly about marginal gains. Where we focus instead is making a shortcut for riders who can only spend one to six hours a week. We can improve these cyclists’ abilities significantly. It’s almost like having a pedal stroke of a professional rider, but with your normal ability to generate power. Oval chainrings can make you simply more efficient with what you can generate, and this is already a very big gain on its own.
In my many years of research experience and testing close to thousand riders of various abilities, I can say that once you become fatigued, your effectiveness and efficiency drop considerably. So, in a sense, oval rings benefit everyone.
Would you like to add anything?
Do your own research, read rider opinions, ask users of oval rings what they think. But nothing will compare to actually trying them yourself. We actually offer a 30-day satisfaction guarantee so there is nothing to lose. Simply try them and have your own opinion.
